Luminescence enhancement in ZnO nanocrystals by polarized light

ZnO nano- and microcrystals produced much enhanced luminescence output when excited by polarized light. The effect of polarized excitation on the intensity and polarization of photoluminescence (PL) of wurtzite ZnO is reported. ZnO nano- and microcrystals (nc and mc) showed up to 18-fold increase in PL intensity when excited with linearly polarized light at 305 nm. The degree of luminescence enhancement was different for different PL peaks and more for ZnO mcs compared to ncs. Time resolved PL decay measurements indicated biexponential decay in 100 μs time scale. The observations suggested that luminescence enhancement depended on polarization selective band to band excitation arising due to crystalline anisotropy and shape asymmetry and subsequent defect related emission.